Density and electrical conductance of the calcium nitrate tetrahydrate + acetamide melt were measured as functions of temperature and mole fi action of acetamide. On the basis of the additivity of molar volume, an alternative method has been suggested for estimating the densities of high- or low-melting anhydrous inorganic and organic salts using a suitable hydrate melt as solvent. Molar conductance data were analyzed by using the Vogel-Tammann-Fulcher equation. At ambient temperature the specific conductance of molten calcium nitrate tetrahydrate decreases by the addition of acetamide as was the case with the addition of KNOB.